Boiler Tuning and Combustion Optimization

An invaluable service offered by Steag Energy Services (formerly ESA) is boiler tuning and optimization. Many boilers are simply not equipped with monitoring and control systems capable of achieving optimum operation. This is a service which our engineers and technical staff are experts in providing.

We conduct an array of operational tests from spatial gaseous analysis to flyash carbon analysis in order to closely monitor boiler operation. A test matrix varying applicable operating parameters such as primary air swirl, overfire air, burner tilt, excess O2, and burners in service, is devised and performed. Through analysis of the collected data, we can determine settings for optimum operation under various conditions. In the past, Steag Energy Services (formerly ESA) has brought power plants within compliance of EPA pollution regulations without installation of any new hardware and without harmful effects to daily operation.

Correcting Existing Final Stoichiometric Imbalances

Local fuel-air imbalances can occur for a number of reasons including windbox restrictions, overfire air duct restrictions or limited port placement, and fuel distribution problems. When operating with reduced excess air these imbalances are revealed by local carbon monoxide (CO) formation. These local CO areas can be significant and affect the average of the entire furnace. A correction in combustion of these local CO spikes can allow reduction of excess air improving emissions and efficiency.

The graphics below show an example of data collected from the economizer outlet plane of a wall-fired unit. The grid measurement shows how the a pocket of high CO effected the overall unit emissions and how elimination of the localized imbalanced improved overall unit emissions.

NOx Optimization through Combustion Staging with Existing Equipment

Many boilers have the capability of operating with lower NOx emissions without installing new equipment. For a given boiler, Steag Energy Services (formerly ESA) can conduct a series of tests to determine the optimum burner settings for reduced NOx operation. On tangentially fired boilers, advanced combustion staging may be achieved through burner out of service selection, limited use of fuel air, increased use of auxiliary and overfire air, and use of burner and overfire air tilts. Advanced combustion staging can be achieved on wall fired boilers through burner out of service selection, inner and outer air register biasing, fuel biasing, and overfire air usage. Steag Energy Services (formerly ESA) can often exceed burner manufactures guarantee points and achievements due to our extensive back-end combustion analysis.

The data in the example data below are from a tangentially fired boiler. A significant nox reduction was achieved through a combination of upper burners out of service and biased upper fuel and aux air dampers.

The next example data are from a tangentially fired unit burning natural gas. NOx reductions were achieved with half of each of the top two most burner levels out of service, reductions in fual air and increases in aux air.

Steag Energy Services (formerly ESA) has also made significant NOx reductions on wall fired units through combustion optimization techniques. The following data is an example the results achieved through alterations in overfire and underfire air, mills in service during full load operation. The optimized operation produced lower NOx and CO at all loads. Over a ten-day period with these settings, average daily NOx went from 0.42 to 0.29 lb/MMBtu.

The final example is from Steag Energy Services's (formerly ESA) optimization efforts on a wall fired unit burning natural gas. Significant opacity (smoke) reductions were achieved through reducing buners in service to a single wall, increasing burner pressure, closing top overfire air ports, opening lower overfire air ports and increasing FGR usage through the windbox.